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Biomedical subjects

A Iwaki

Publications and source records attributed to A Iwaki.

At least 37 records · Page 2Linked to original sources
PubMed1993

Epitope mapping and characterization of monoclonal antibodies to human protein C.

Six monoclonal antibodies specific to human protein C were characterized. Epitopes of these antibodies were determined on isolated proteolytic peptides of protein C by immunological methods. Three antibodies bound light chain of protein C: PC01 bound the gamma-carboxyglutamic acid domain calcium-dependently, while PC02 and PC08 bound the first epidermal growth factor-like domain in calcium-dependent and independent manners, respectively. The other three antibodies bound the heavy chain of protein C: PC13 bound activation peptide, PC04 recognized the activation site and PC09 bound the region close to a disulfide bond connecting light and heavy chains. Activation of protein C with thrombin-thrombomodulin complex was inhibited strongly by PC04 and moderately by PC08, PC09 and PC13. PC04 and PC13 may directly block the activation site. On the other hand, epitopes of PC08 and PC09 may be involved in interaction between protein C and thrombin-thrombomodulin complex, or locate close to activation site on the tertiary structure of protein C. Anticlotting activity of protein C was inhibited strongly by PC01 and moderately by PC02, PC08 and PC09, while amidolytic activity was inhibited only by PC09. The epitopes described here may constitute part of protein-C-specific sites, which are important for the function of protein C.

Amino Acid Sequence↗
PubMed1993

Alpha B-crystallin in oxidative muscle fibers and its accumulation in ragged-red fibers: a comparative immunohistochemical and histochemical study in human skeletal muscle.

The alpha B-crystallin gene is abundantly expressed in the vertebrate lens and at lower levels in various non-lenticular tissues. Among the non-lenticular tissues, alpha B-crystallin is present at high levels in the heart and skeletal muscle. Using a specific antibody against alpha B-crystallin, the cellular localization of alpha B-crystallin was studied in biopsies of human skeletal muscles. Expression of alpha B-crystallin was observed in normal oxidative muscle fibers that show positive reactions for NADH-tetrazolium reductase and cytochrome c oxidase. In muscle diseases increased immunoreactivity for alpha B-crystallin was found in ragged-red fibers, which stained darkly with histochemistry for succinate dehydrogenase. Since alpha B-crystallin is related to small heat-shock proteins and can be induced by various stress conditions, the increased alpha B-crystallin immunoreactivity of ragged-red fibers could result from profound oxidative stress produced by the abnormal mitochondrial metabolism.

Adult↗
PubMed1993

A missense mutation in the proteolipid protein gene responsible for Pelizaeus-Merzbacher disease in a Japanese family.

We investigated the proteolipid protein (PLP) gene of two boys in a Japanese family with Pelizaeus-Merzbacher disease (PMD), an X-linked neurologic disorder characterized by dysmyelination in the central nervous system (CNS). The patients showed similar clinical signs from birth and autopsy on the elder brother confirmed a connatal type of PMD. Direct sequencing of the PLP gene and PLP mRNAs from the brain of the PMD patient revealed a G to T transition in exon V of the PLP gene, which leads to a glycine to cysteine substitution at residue 220. Allele-specific oligonucleotide hybridization revealed that this mutation was also present in his brother, but was absent in 100 X chromosomes of normal Japanese individuals. Northern blot analysis showed that the mRNA levels of PLP and myelin basic protein, two major myelin proteins produced by oligodendrocytes, were much reduced in the PMD brain, hence, there was a specific loss of oligodendrocytes. It seems likely that the substitution is responsible for PMD (connatal type) in this particular family and causes oligodendrocytes death in the CNS.

Adolescent↗
PubMed1993

A novel insertional mutation at exon VII of the myelin proteolipid protein gene in Pelizaeus-Merzbacher disease.

Pelizaeus-Merzbacher disease (PMD) is an X-linked neurological disorder characterized by dysmyelination in the central nervous system (CNS). Recently mutations of the myelin proteolipid protein (PLP) gene which encodes both PLP and its isoform, DM-20 generated by alternative splicing, have been demonstrated in PMD patients. We analyzed the seven exons of the PLP gene of a Japanese boy affected with PMD by direct sequencing and identified an insertion event in exon VII of the PLP gene. This mutation was also present in his carrier mother, but was absent in ninety-five X chromosomes of normal Japanese. The frame-shift mutation leads to the production of truncated PLP with altered carboxyl terminal amino acid sequences, resulting in considerable change of the structure of PLP and DM-20 necessary for functional purposes. This is the first report of a mutation in exon VII of the PLP gene associated with PMD.

Adolescent↗
PubMed1993

Alpha B-crystallin and 27-kd heat shock protein are regulated by stress conditions in the central nervous system and accumulate in Rosenthal fibers.

To understand the significance of the accumulation of alpha B-crystallin in Rosenthal fibers within astrocytes, the expression and metabolism of alpha B-crystallin in glioma cell lines were examined under the conditions of heat and oxidative stress. alpha B-crystallin mRNA was increased after both stresses, and alpha B-crystallin protein moved from a detergent-soluble to a detergent-insoluble form. In addition, Western blotting of Alexander's disease brain homogenates revealed that the 27-kd heat shock protein (HSP27), which is related to alpha B-crystallin, accumulates along with alpha B-crystallin. The presence of HSP27 in Rosenthal fibers was directly demonstrated by immunohistochemistry. Our results suggest that astrocytes in Alexander's disease may be involved in an as yet unknown kind of stress reaction that causes the accumulation of alpha B-crystallin and HSP27 and results in Rosenthal fiber formation.

Animals↗
PubMed1992

Accumulation of alpha B-crystallin in brains of patients with Alexander's disease is not due to an abnormality of the 5'-flanking and coding sequence of the genomic DNA.

alpha B-Crystallin is a major protein component of Rosenthal fibers, which massively accumulate in the brains of patients suffering from Alexander's disease. To examine whether or not accumulation of alpha B-crystallin is due to any abnormality of the gene structures, we determined the sequence of the alpha B-crystallin gene in two cases of pathologically confirmed Alexander's disease. Direct sequencing of the promoter and coding regions of the alpha B-crystallin gene in patients revealed them to have a normal sequence. Northern blotting showed a single alpha B-crystallin mRNA species expressed in the Alexander's disease brain.

Aged↗
PubMed1992

Accumulation of alpha B-crystallin in central nervous system glia and neurons in pathologic conditions.

Alpha B-crystallin, a major protein of the vertebrate lens, is found in the central nervous system (CNS) and is a major protein component of Rosenthal fibers (RF), intracytoplasmic inclusions within astrocytes. Its level of expression in the normal CNS is low and appears to be confined to glial cells, both astrocytes and oligodendrocytes. A number of human brains displaying a variety of pathologic changes were examined by immunohistochemistry with an anti-alpha B-crystallin antiserum and increased immunoreactivity was found in astrocytes and oligodendrocytes without the formation of RFs. Furthermore, some neurons in neurodegenerative disorders were also immunolabeled with the anti-alpha B-crystallin antiserum. Thus, the accumulation of alpha B-crystallin appears to be part of the repertoire of reactive processes of CNS glial cells and some neurons in pathologic conditions.

Animals↗
PubMed1991

Preferential expression of alpha B-crystallin in astrocytic elements of neuroectodermal tumors.

Recently the authors have identified a major component of Rosenthal fibers as alpha B-crystallin, a major lens protein. In the current study the authors investigated the expression of alpha B-crystallin in four cultured glioma cell lines and in 115 human neuroectodermal tumors. alpha B-crystallin was expressed differentially by those glioma cell lines, but not by neuroblastoma cell lines. Northern blot analysis revealed two distinct messages for alpha B-crystallin in C-6, whereas only a single message in U-373MG and G26-24. In human surgical specimens positive immunostaining was frequently observed in the following brain tumors: pilocytic astrocytoma of the juvenile type, anaplastic astrocytoma, glioblastoma multiforme, and subependymal giant cell astrocytoma. The astrocytic elements of mixed oligoastrocytomas, glioblastomas with sarcomatous components, and gangliogliomas were likewise strongly stained. In contrast, little immunoreactivity was observed in ependymal and choroid plexus tumors. Thus, alpha B-crystallin is mainly expressed by astrocytic tumors among neuroectodermal neoplasms, without regard to the presence of Rosenthal fibers.

Blotting, Northern↗
PubMed1991

Expression of alpha B-crystallin in the developing rat kidney.

The expression and cellular localization of alpha B-crystallin during rat renal development was studied by Northern blot analysis and by immunocytochemistry. Northern blotting of total RNA extracted from whole kidneys revealed that the messenger RNA for alpha B-crystallin rapidly increased after birth to reach adult levels by 20 days. At the same time, immunohistochemistry for alpha B-crystallin demonstrated that the prominent elongation of Henle's loop during the first 10 days of life was accompanied by increased alpha B-crystallin expression. Thus, the development of alpha B-crystallin expression is correlated temporally with the acquisition of tubule function in early post-natal life.

Animals↗
PubMed1991

Rosenthal fibers share epitopes with alpha B-crystallin, glial fibrillary acidic protein, and ubiquitin, but not with vimentin. Immunoelectron microscopy with colloidal gold.

Ultrastructural immunoreactivities of alpha B-crystallin, glial fibrillary acidic protein (GFAP), ubiquitin, and vimentin in Rosenthal fibers (RFs) isolated from an Alexander's disease brain were investigated using nonosmium and low-temperature embedding technique. The morphology of RFs embedded in Lowicryl K4M resin was well preserved after treatment with 0.5% Triton X-100. alpha B-crystallin immunoreactivity was present in RFs of various sizes and was the strongest in loosely scattered deposits, which were considered to be the initial stage of RFs. Glial fibrillary acidic protein immunoreactivity in RFs was heavy, homogeneous throughout RFs, and equivalent to that in networks of glial filaments. Immunoreactivities of both alpha B-crystallin and GFAP were mainly restricted to the high electron-dense areas within RFs and were proved to exist close to each other by double immunolabeling. Rosenthal fibers were negative for vimentin. Ubiquitin immunoreactivity was relatively homogeneous in RFs with small diameters, but in RFs with large diameters, the immunoreactivity diminished in the center. Based on these observations, combined with the tendency of self-aggregation of alpha B-crystallin, it is conceivable that RFs are huge aggregation products of alpha B-crystallin involving GFAP, and that ubiquitination may be a consequent phenomenon, as it may be in other intracytoplasmic inclusions, such as neurofibrillary tangles and Lewy bodies.

Brain↗
PubMed1990

Multiple mRNAs of rat brain alpha-crystallin B chain result from alternative transcriptional initiation.

Two major classes of mRNAs for the alpha-crystallin B chain (or alpha(B)crystallin), about 0.9 and 1.2 kilobases in length, are expressed in rat brain. To examine the structures of these mRNAs, we isolated cDNA clones from rat brain and genomic DNA from rat liver. Characterization of these clones as well as Northern blot analysis indicated that the various mRNAs differed in the lengths of their 5' leader sequences. RNase protection assays revealed that the gene for alpha-crystallin B chain contains multiple start sites. The transcriptional start sites of the longer mRNAs are preceded by a putative CAAT box and that of the shorter mRNA by a putative TATA box. The shorter mRNA encodes the alpha-crystallin B chain protein, whereas the longer mRNA contained three extra small open reading frames upstream of the AUG start codon for the protein. The shorter mRNA is abundant in lens, heart, muscle, and kidney, while the longer mRNAs are constitutively expressed at low levels in a wide variety of tissues. The shorter mRNA was increased by treatment with phorbol 12-myristate 13-acetate in rat C6 glioma cells. Since there is only a single copy of the alpha-crystallin B chain gene, our results indicate that the two classes of mRNAs are generated by alternative transcriptional initiation from different promoters and their expressions are regulated differentially.

Amino Acid Sequence↗
PubMed1979

Remnant liver function during surgery for extensive hepatic resection.

True functional reserve of remnant liver should be determined at the same condition that contemplated hepatectomy has been performed, and this condition can be achieved before resection by temporary clamping of the inflow vessels of hepatic lobes to be removed. Using indocyanine green (ICG), the remnant liver function (RLF) was evaluated whether or not the method can be a useful indicator for or against hepatomy. In the study of healthy dogs, the RLF proved to be a reliable indicator to prospect hepatic failure which may occur after extensive resection of the liver. Then, the method was employed in nine patients who underwent 40 to 70 per cent hepatectomy. The results indicated that the RLF with ICG during surgery, if performed under stable hemodynamics, is a beneficial tool to decide the resectability in equivocal cases.

Adult↗
PubMed1978

Effect of 5-fluorouracil on liver regeneration and metabolism after partial hepatectomy in the rat.

The effects of 5-fluorouracil (5-FU) on regenerating liver were studied after two thirds hepatectomy in rats. In Group I, 68% hepatectomy was performed. In Group II, 5-FU in a dose of 20 mg/kg was administered intravenously immediately after, 24 and 48 hours after the same hepatectomy. In Group III, the same amount of 5-FU was given after sham-operation. The mortality rates were 4.5% in Group I, 28.0% in Group II, and 0% in Group III. The treatment with 5-FU following hepatectomy caused not only suppression but delay of liver cell division. Histologic changes such as cellular degeneration, liver steatosis and dilatation of the sinusoidal space were marked and prolonged in the hepatectomy-5-FU group. The metabolic abnormalities in albumin, cholesterol, triglycedides, and phospholipids were further more profound in Group II compared to those in Group I. In Group III, moderate derangements in albumin, triglycerides and phospholipids were observed. The results may indicate that adjuvant chemotherapy with 5-FU or similar drugs immediately after partial hepatectomy in hepatoma patients should be performed with great care if necessary. Otherwise, it should not be carried out until hepatic regneration is almost completed.

Animals↗